JP2005186110A - Protecting sheet for laser beam processing and method for producing laser beam processed product using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a protecting sheet for laser beam processing with which in the case of processing a material to be processed with an ultraviolet absorption ablation in the laser beam, the contamination of the material surface to be processed with decomposed material can effectively be restrained, and a method for producing a laser beam processed product using the protecting sheet for laser beam processing. <P>SOLUTION: The protecting sheet for laser beam processing is the one arranged at the incident surface side of the material to be processed when the material to be processed is processed with the ultraviolet absorption ablation in the laser beam. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a protective sheet for laser processing used when processing a workpiece by ultraviolet absorption ablation of laser light. In addition, the present invention is applicable to various processing such as sheet materials, circuit boards, semiconductor wafers, glass substrates, ceramic substrates, metal substrates, light emitting or receiving element substrates such as semiconductor lasers, MEMS substrates, semiconductor packages, cloth, leather, or paper. The present invention relates to a method of manufacturing a laser processed product obtained by subjecting an object to shape processing such as cutting, drilling, marking, grooving, scribing, or trimming by ultraviolet absorption ablation of laser light.

  With the recent miniaturization of electrical and electronic equipment, parts are becoming smaller and higher definition. For this reason, high-definition and high-precision processing with an accuracy of ± 50 μm or less has been demanded for external processing of various materials. However, the conventional punching process such as press working has an accuracy of about ± 100 μm at most, and cannot meet the recent demand for higher precision. Also, high-definition and high-precision are required for drilling various materials, and it has become impossible to perform drilling with conventional drills or dies.

  In recent years, various methods for processing various materials using laser light have attracted attention as a solution. In particular, a processing method by ultraviolet absorption ablation of laser light, which has low thermal damage and enables high-definition processing, has attracted attention as a precise outer shape processing method and a fine drilling method.

  As the above technique, for example, as a method for dicing a workpiece, a method is proposed in which the workpiece is supported and fixed on a dicing sheet and the workpiece is diced with a laser beam (Patent Document 1). A method of dicing a semiconductor wafer by combining a water microjet and a laser has also been proposed (Patent Document 2). The dicing sheet described in the patent document is provided on the laser beam emitting surface side of the workpiece, and is used for supporting and fixing the workpiece (laser processed product) during dicing and in each subsequent process. .

By the way, when laser light is used, decomposition products such as carbon generated during laser processing adhere to the surface of the workpiece, and thus a post-treatment called desmear is necessary to remove it. Since the adhesion strength of the decomposed product becomes stronger in proportion to the power of the laser beam, there is a problem that it becomes difficult to remove the decomposed product in the post-treatment when the power of the laser beam is increased. In particular, the surface side (laser light emitting surface side) of the workpiece that contacts the processing table or the adhesive sheet is not only the decomposed product of the workpiece, but also the processed table or adhesive sheet decomposed product by laser light irradiation. There is a tendency to adhere firmly to the surface. Therefore, there existed a problem that the improvement of the through-put of a process was prevented or the reliability of a cutting | disconnection and drilling was reduced.
JP 2002-343747 A JP 2003-34780 A

  It is an object of the present invention to provide a protective sheet for laser processing capable of effectively suppressing contamination of the surface of the workpiece due to a decomposition product when processing the workpiece by ultraviolet absorption ablation of laser light. To do. It is another object of the present invention to provide a method for producing a laser processed product using the laser processing protective sheet.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above object can be achieved by the following protective sheet for laser processing (hereinafter also referred to as protective sheet), and have completed the present invention.

  That is, the present invention relates to a protective sheet for laser processing provided on the laser light incident surface side of a workpiece when processing the workpiece by ultraviolet absorption ablation of laser light.

  The protective sheet is laminated on the laser beam incident surface side (laser beam irradiation surface side) of the workpiece before laser processing the workpiece by ultraviolet absorption ablation of laser beam, and decomposed products and scattering generated by ablation. It is used to protect the workpiece surface from the object. And a protection sheet is processed with a to-be-processed object by the ultraviolet absorption ablation of a laser beam. By using the protective sheet, the decomposed material generated from the laser light irradiation part adheres to the surface of the protective sheet covering the workpiece, effectively preventing the decomposed material from adhering to the surface of the workpiece. can do.

  The protective sheet preferably has a light transmittance of less than 50% in the laser light absorption region. By using a protective sheet having a light transmittance of less than 50%, it is possible to effectively prevent decomposition products from entering the interface between the protection sheet and the workpiece and attaching the decomposition products to the interface portion. it can. As a result, not only can the protective sheet be easily peeled off from the workpiece after laser processing, but also the laser processing accuracy of the workpiece can be improved.

  The reason why the interface portion can be prevented from being contaminated by the decomposition product by using the protective sheet is considered as follows. When the light transmittance in the laser light absorption region of the protective sheet is less than 50%, the protective sheet is eroded by the laser light before the workpiece because the laser sheet has a high efficiency of laser energy utilization. The underlying workpiece is eroded after the laser beam irradiation part of the protective sheet is eroded, but the decomposed material of the workpiece is efficiently scattered outside from the eroded part of the protective sheet. It is considered that contamination at the interface with the workpiece can be suppressed.

  The light transmittance in the laser light absorption region of the protective sheet is preferably 40% or less, more preferably 30% or less, and particularly preferably 0%. When the light transmittance is 50% or more, energy transmission to the workpiece, which is a light energy absorber, increases, and before the protective sheet is eroded by the laser light, the laser light transmitted through the protective sheet Work piece erosion tends to progress. In that case, since there is no scattering path of the decomposition product generated by the erosion of the workpiece, it is considered that the decomposition product enters between the protective sheet and the workpiece and contaminates the workpiece surface. In other words, unless the protective sheet is broken or drilled by laser ablation, the gas pressure at the time of decomposition of the workpiece is high, so that the gaseous decomposition product stays between the protection sheet and the workpiece, and the decomposition product is processed. It will contaminate the object surface. If the workpiece surface is contaminated with decomposition products as described above, it becomes difficult to peel off the protective sheet from the workpiece after laser processing the workpiece, or removal of decomposition products in post-processing is difficult. It tends to be difficult and the processing accuracy of the workpiece tends to decrease.

  It is preferable that the said protective sheet is what is provided with the adhesive layer on the base material. By imparting adhesiveness to the protective sheet, it is possible to improve the adhesion of the interface between the protective sheet and the workpiece, so that the entry of the decomposed product into the interface can be suppressed, and as a result, It becomes possible to suppress contamination of the workpiece surface.

  Moreover, in this invention, it is preferable that the said base material contains an aromatic polymer. By using an aromatic polymer as the material for forming the base material, the light transmittance in the laser light absorption region can be reduced, and the etching rate of the protective sheet can be increased.

  Further, the weight ratio of the aromatic ring in the repeating unit constituting the aromatic polymer is preferably 41% by weight or more, and more preferably 50% by weight or more. If the weight ratio of the aromatic ring is less than 41% by weight, the light transmittance in the laser light absorption region cannot be made sufficiently small, and thus it tends to be difficult to sufficiently increase the etching rate of the protective sheet. .

  The present invention also includes a step (1) of installing the protective sheet for laser processing on the laser beam incident surface side of the workpiece, and a step of processing the protective sheet for laser processing and the workpiece by irradiating the laser beam ( 2) The present invention relates to a method for producing a laser-processed product including a step (3) of peeling off a protective sheet for laser processing from a processed workpiece.

  The workpiece is preferably a sheet material, a circuit board, a semiconductor wafer, a glass substrate, a ceramic substrate, a metal substrate, a semiconductor laser light emitting or receiving element substrate, a MEMS substrate, or a semiconductor package. Moreover, it is preferable that the said process is a process which cuts or drills a to-be-processed object.

  The protective sheet of the present invention is preferably used particularly when a semiconductor chip is produced by dicing a semiconductor wafer.

  The laser used in the present invention is non-thermal processing that does not go through a thermal processing process in order not to deteriorate the precision and appearance of the hole edge and the cutting wall surface of the workpiece due to thermal damage during laser processing. Use a laser that can be ablated by absorbing ultraviolet light. In particular, it is preferable to use a laser capable of condensing laser light in a narrow width of 20 μm or less and emitting ultraviolet light of 400 nm or less.

Specifically, a laser having an oscillation wavelength of 400 nm or less, for example, a KrF excimer laser with an oscillation wavelength of 248 nm, a 308 nm XeCI excimer laser, a third harmonic (355 nm) or a fourth harmonic (266 nm) of a YAG laser, or In the case of a laser having a wavelength of 400 nm or more, a wavelength of 750 to 800 nm that can absorb light in the ultraviolet region through a multiphoton absorption process and can be cut to a width of 20 μm or less by multiphoton absorption ablation. Examples thereof include a laser having a pulse width of 1e- ⁹ seconds (0.000000001 seconds) or less using a nearby titanium sapphire laser.

  The workpiece is not particularly limited as long as it can be processed by ultraviolet absorption ablation of the laser beam output by the laser, and examples thereof include various sheet materials, circuit boards, semiconductor wafers, glass substrates, ceramic substrates. And a light emitting or light receiving element substrate such as a metal substrate, a semiconductor laser, a MEMS (Micro Electro Mechanical System) substrate, a semiconductor package, cloth, leather, and paper.

  The protective sheet of the present invention can be suitably used particularly for processing a sheet material, a circuit board, a semiconductor wafer, a glass substrate, a ceramic substrate, a metal substrate, a semiconductor laser light emitting or receiving element substrate, a MEMS substrate, or a semiconductor package. .

  Examples of the various sheet materials include polyimide resins, polyester resins, epoxy resins, urethane resins, polystyrene resins, polyethylene resins, polyamide resins, polycarbonate resins, silicone resins, and fluorine resins. Polymer films and nonwoven fabrics composed of, etc., sheets obtained by stretching or impregnating those resins with physical or optical functions, metal sheets such as copper, aluminum, stainless steel, or the above polymer films and / or Examples include a metal sheet laminated directly or via an adhesive.

  Examples of the circuit board include a single-sided, double-sided or multilayer flexible printed board, a rigid board made of glass epoxy, ceramic, or metal core board, an optical circuit formed on glass or polymer, or an opto-electric hybrid circuit board. It is done.

  The protective sheet of the present invention is a sheet used when processing a workpiece by ultraviolet absorption ablation of laser light. The protective sheet preferably has a light transmittance of less than 50% in a laser light (ultraviolet) absorption region. The protective sheet may be formed only from a base material, and the adhesive layer may be provided on the base material.

  Examples of the base material include polyethylene terephthalate, polyethylene naphthalate, polystyrene, polycarbonate, polyimide, (meth) acrylic polymer, polyurethane, and polyolefin polymers such as polyethylene, polypropylene, and polyethylene oxide. It is not limited to these. Among these, it is preferable to use an aromatic polymer, and it is particularly preferable to use polyimide, polyethylene naphthalate, or polycarbonate.

  It is preferable to add a filler to the substrate. The filler is a material added to make the light transmittance of the laser light absorption region less than 50%. For example, pigment, dye, dye, Au, Cu, Pt, Ag and other metal fine particles, and metal colloid And inorganic fine particles such as carbon.

  The dye only needs to absorb light having a specific wavelength of the laser to be used. As the dye, various dyes such as a basic dye, an acid dye, and a direct dye can be used. Examples of the dye or pigment include nitro dye, nitroso dye, stilbene dye, pyrazolone dye, thiazole dye, azo dye, polyazo dye, carbonium dye, quinoanyl dye, indophenol dye, indoaniline dye, indamine dye, quinoneimine dye, Azine dye, oxidation dye, oxazine dye, thiazine dye, acridine dye, diphenylmethane dye, triphenylmethane dye, xanthene dye, thioxanthene dye, sulfur dye, pyridine dye, pyridone dye, thiadiazole dye, thiophene dye, benzoisothiazole dye, Dicyanoimidazole dye, benzopyran dye, benzodifuranone dye, quinoline dye, indigo dye, thioindigo dye, anthraquinone dye, benzophenone dye, benzoquinone dye, naphtho Examples include quinone dyes, phthalocyanine dyes, cyanine dyes, methine dyes, polymethine dyes, azomethine dyes, condensed methine dyes, naphthalimide dyes, perinone dyes, triarylmethane dyes, xanthene dyes, aminoketone dyes, oxyketone dyes, and indigoid dyes. . These may be used alone or in combination of two or more.

  The dye or pigment may be a nonlinear optical pigment. The nonlinear optical dye is not particularly limited, and is a known nonlinear optical dye (for example, benzene-based nonlinear optical dye, stilbene-based nonlinear optical dye, cyanine-based nonlinear optical dye, azo-based nonlinear optical dye, rhodamine-based nonlinear optical dye, biphenyl). Non-linear optical dyes, chalcone non-linear optical dyes, and cyanocinnamic acid non-linear optical dyes).

  Furthermore, as the dye or pigment, a so-called “functional pigment” can also be used. The functional dye is composed of, for example, a carrier generating material and a carrier transfer material. Examples of the carrier generating material include perylene pigments, quinone pigments, squarylium dyes, azurenium dyes, thiapyrylium dyes, bisazo pigments, and the like. Examples of the carrier transfer material include oxadiazole derivatives, oxazole derivatives, pyrazoline derivatives, hydrazone derivatives, and arylamine derivatives.

  The amount of the filler added can be appropriately adjusted depending on the light transmittance of the base polymer used, but is usually about 5 parts by weight, preferably about 3 parts by weight, based on 100 parts by weight of the base polymer. .

  The substrate may be a single layer or a multilayer. Moreover, various shapes, such as a film | membrane form and a mesh form, can be taken.

  The thickness of the base material is appropriately adjusted within a range that does not impair the operability and workability in each process such as bonding onto the work piece, cutting and punching of the work piece, and peeling and recovery of the cut piece. However, it is usually 500 μm or less, preferably about 3 to 300 μm, and more preferably 5 to 250 μm. The surface of the substrate is chemically treated with conventional surface treatments such as chromic acid treatment, ozone exposure, flame exposure, high piezoelectric impact exposure, and ionizing radiation treatment to enhance adhesion, retention, etc. with adjacent materials. Alternatively, physical treatment may be performed.

  As a material for forming the pressure-sensitive adhesive layer, known pressure-sensitive adhesives including (meth) acrylic polymers and rubber-based polymers can be used.

  Examples of the monomer component for forming the (meth) acrylic polymer include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a t-butyl group, an isobutyl group, an amyl group, an isoamyl group, and a hexyl group. Group, heptyl group, cyclohexyl group, 2-ethylhexyl group, octyl group, isooctyl group, nonyl group, isononyl group, decyl group, isodecyl group, undecyl group, lauryl group, tridecyl group, tetradecyl group, stearyl group, octadecyl group, and Examples thereof include alkyl (meth) acrylates having a linear or branched alkyl group having 30 or less carbon atoms, preferably 4 to 18 carbon atoms, such as a dodecyl group. These alkyl (meth) acrylates may be used alone or in combination of two or more.

  Other monomer components include, for example, acrylic acid, methacrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid-containing monomers, anhydrous Acid anhydride monomers such as maleic acid and itaconic anhydride, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6- (meth) acrylic acid Hydroxyl groups such as hydroxyhexyl, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, and (4-hydroxymethylcyclohexyl) methyl (meth) acrylate Contains Nomers, styrene sulfonic acid, allyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate, and (meth) acryloyloxynaphthalene sulfonic acid Examples thereof include sulfonic acid group-containing monomers and phosphoric acid group-containing monomers such as 2-hydroxyethylacryloyl phosphate. These monomer components may be used alone or in combination of two or more.

  Moreover, a polyfunctional monomer etc. can also be used as a copolymerization monomer component as needed for the purpose of a crosslinking treatment of a (meth) acrylic polymer.

  Examples of polyfunctional monomers include hexanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and pentaerythritol di (Meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol monohydroxypenta (meth) acrylate, Dipentaerythritol hexa (meth) acrylate, epoxy (meth) acrylate, polyester (meth) acrylate, and urethane (meth) acrylate Etc., and the like. These polyfunctional monomers may be used individually by 1 type, and may use 2 or more types together.

  The amount of the polyfunctional monomer used is preferably 30% by weight or less, more preferably 20% by weight or less of the total monomer components from the viewpoint of adhesive properties and the like.

  For the preparation of the (meth) acrylic polymer, an appropriate method such as a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, or a suspension polymerization method is applied to a mixture containing one or more monomer components. It can be carried out.

  Examples of the polymerization initiator include peroxides such as hydrogen peroxide, benzoyl peroxide, and t-butyl peroxide. Although it is desirable to use it alone, it can also be used as a redox polymerization initiator in combination with a reducing agent. Examples of the reducing agent include ionized salts such as sulfites, hydrogen sulfites, iron, copper, and cobalt salts, amines such as triethanolamine, and reducing sugars such as aldose and ketose. Azo compounds are also preferred polymerization initiators, and are 2,2′-azobis-2-methylpropioamidine, 2,2′-azobis-2,4-dimethylvaleronitrile, 2,2′-azobis- Use N, N'-dimethyleneisobutylaminate, 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methyl-N- (2-hydroxyethyl) propionamide, etc. Can do. It is also possible to use two or more of the above polymerization initiators in combination.

  The reaction temperature is usually about 50 to 85 ° C., and the reaction time is about 1 to 8 hours. Among the production methods, a solution polymerization method is preferable, and a polar solvent such as ethyl acetate or toluene is generally used as a solvent for the (meth) acrylic polymer. The solution concentration is usually about 20 to 80% by weight.

  In order to increase the number average molecular weight of the (meth) acrylic polymer that is the base polymer, a crosslinking agent can be appropriately added to the pressure-sensitive adhesive. Examples of the crosslinking agent include polyisocyanate compounds, epoxy compounds, aziridine compounds, melamine resins, urea resins, anhydrous compounds, polyamines, and carboxyl group-containing polymers. In the case of using a crosslinking agent, the amount used is considered to be about 0.01 to 5 parts by weight with respect to 100 parts by weight of the base polymer, considering that the peeling adhesive strength does not decrease too much. Is preferred. In addition to the above-described components, the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer may include conventional additives such as various conventionally known tackifiers, anti-aging agents, fillers, anti-aging agents, and coloring agents. It can be included.

  In order to improve the peelability from the workpiece, the pressure-sensitive adhesive is preferably a radiation-curable pressure-sensitive adhesive that is cured by radiation such as ultraviolet rays or electron beams. In addition, when using a radiation curing type adhesive as an adhesive, since the radiation is irradiated to an adhesive layer after a laser processing, the said base material has sufficient radiolucency.

  As the radiation curable pressure-sensitive adhesive, those having a radiation curable functional group such as a carbon-carbon double bond and exhibiting adhesiveness can be used without particular limitation. Examples of the radiation curable pressure-sensitive adhesive include a radiation curable pressure-sensitive adhesive obtained by blending the aforementioned (meth) acrylic polymer with a radiation curable monomer component or oligomer component.

  Examples of the radiation curable monomer component and oligomer component to be blended include urethane (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethanetetra (meth) acrylate, pentaerythritol tri (meth) acrylate, and pentaerythritol. Examples include tetra (meth) acrylate, dipentaerythritol monohydroxypenta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and 1,4-butylene glycol di (meth) acrylate. These may be used alone or in combination of two or more.

  The blending amount of the radiation curable monomer component or oligomer component is not particularly limited, but in consideration of the tackiness, it is based on 100 parts by weight of the base polymer such as a (meth) acrylic polymer constituting the pressure sensitive adhesive. The amount is preferably about 5 to 500 parts by weight, and more preferably about 70 to 150 parts by weight.

  Moreover, as a radiation curable adhesive, what has a carbon-carbon double bond in a polymer side chain or a principal chain, or the principal chain terminal can also be used as a base polymer. As such a base polymer, a polymer having a (meth) acrylic polymer as a basic skeleton is preferable. In this case, it is not necessary to add a radiation curable monomer component or oligomer component, and its use is optional.

  The radiation curable pressure-sensitive adhesive contains a photopolymerization initiator when cured by ultraviolet rays or the like. Examples of the photopolymerization initiator include 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone, α-hydroxy-α, α-methylacetophenone, methoxyacetophenone, and 2,2-dimethoxy-2-phenyl. Acetophenone compounds such as acetophenone, 2,2-diethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropane-1, benzoin ethyl ether, benzoin isopropyl Benzoin ether compounds such as ether and anisoin methyl ether, α-ketol compounds such as 2-methyl-2-hydroxypropylphenone, ketal compounds such as benzyldimethyl ketal, 2-naphthalenesulfonyl chloride Aromatic sulfonyl chloride compounds such as Lido, photoactive oxime compounds such as 1-phenone-1,1-propanedione-2- (o-ethoxycarbonyl) oxime, benzophenone, benzoylbenzoic acid, 3,3′-dimethyl Benzophenone compounds such as -4-methoxybenzophenone, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2 Thioxanthone compounds such as 1,4-diethylthioxanthone and 2,4-diisopropylthioxanthone, camphorquinone, halogenated ketone, acyl phosphinoxide and acyl phosphonate.

  The blending amount of the photopolymerization initiator is preferably about 0.1 to 10 parts by weight, more preferably about 0.1 to 10 parts by weight with respect to 100 parts by weight of the base polymer such as (meth) acrylic polymer constituting the pressure-sensitive adhesive. About 5 to 5 parts by weight.

  The protective sheet of the present invention can be produced, for example, by applying a pressure-sensitive adhesive solution to the surface of a substrate and drying (by heat-crosslinking as necessary) to form a pressure-sensitive adhesive layer. Moreover, after forming an adhesive layer in a release liner separately, the method of bonding it to a base material etc. are employable. If necessary, a separator may be provided on the surface of the pressure-sensitive adhesive layer.

  The pressure-sensitive adhesive layer preferably has a low content of low molecular weight substances from the viewpoint of preventing contamination of the workpiece. From this point, the number average molecular weight of the (meth) acrylic polymer is preferably 300,000 or more, more preferably 400,000 to 3,000,000.

  Although the thickness of an adhesive layer can be suitably selected in the range which does not peel from a workpiece, it is about 5-300 micrometers normally, Preferably it is about 10-100 micrometers, More preferably, it is about 20-50 micrometers.

  Further, the adhesive strength of the pressure-sensitive adhesive layer is preferably 20 N / 20 mm or less, more preferably based on the adhesive strength (90-degree peel value, peeling speed 300 mm / min) at normal temperature (before laser irradiation) to SUS304. 0.001 to 10 N / 20 mm, particularly preferably 0.01 to 8 N / 20 mm.

  The said separator is provided as needed in order to protect a label process or an adhesive layer. Examples of the constituent material of the separator include paper, polyethylene, polypropylene, and synthetic resin films such as polyethylene terephthalate. The surface of the separator may be subjected to release treatment such as silicone treatment, long-chain alkyl treatment, fluorine treatment, etc., as necessary, in order to enhance the peelability from the pressure-sensitive adhesive layer. Further, if necessary, an ultraviolet transmission preventing treatment or the like may be performed so that the protective sheet does not react with environmental ultraviolet rays. The thickness of a separator is 10-200 micrometers normally, Preferably it is about 25-100 micrometers.

  Hereinafter, a method for manufacturing a laser processed product by ultraviolet absorption ablation of laser light using the protective sheet of the present invention will be described. For example, in the case of cutting processing, as shown in FIGS. 1 and 3, the protective sheet 2, the workpiece 1, and the adhesive sheet 3 are bonded together by a known means such as a roll laminator or a press. The object-adhesive sheet laminate 4 is arranged on the suction plate 6 of the suction stage 5, and the laser beam 7 output from a predetermined laser oscillator is condensed on the laminate 4 by the lens on the protective sheet 2. While irradiating, cutting processing is performed by moving the laser irradiation position along a predetermined processing line. The pressure-sensitive adhesive sheet 3 provided on the laser beam emitting surface side of the workpiece plays a role of supporting and fixing the workpiece before laser processing, and plays a role of preventing the cut material from falling after the laser processing. A sheet with low laser processability is used. As the pressure-sensitive adhesive sheet 3, a general sheet in which a pressure-sensitive adhesive layer is laminated on a substrate can be used without particular limitation.

  As the laser beam moving means, a known laser processing method such as a galvano scan, an XY stage scan, or a mask imaging process is used.

  The laser processing conditions are not particularly limited as long as the protective sheet 2 and the workpiece 1 are completely cut, but the workpiece 1 is cut in order to avoid cutting up to the adhesive sheet 3. It is preferable to be within twice the energy condition.

In addition, the cutting margin (cutting groove) can be narrowed by narrowing the beam diameter of the laser beam condensing part.
It is preferable that the beam diameter (μm)> 2 × (laser beam moving speed (μm / sec) / laser beam repetition frequency (Hz)) is satisfied.

  Further, in the case of drilling, as shown in FIG. 2, a protective sheet obtained by bonding the protective sheet 2, the workpiece 1 and the adhesive sheet 3 by a known means such as a roll laminator or a press-workpiece- The pressure-sensitive adhesive sheet laminate 4 is disposed on the suction plate 6 of the suction stage 5, and laser light 7 output from a predetermined laser oscillator is condensed and irradiated on the protective sheet 2 by a lens on the laminate 4. To form holes.

  The hole is formed by a known laser processing method such as galvano scan, XY stage scan, or punching by mask imaging. The optimum laser processing condition may be determined based on the ablation threshold of the material to be processed.

  Further, by blowing a gas such as helium, nitrogen, oxygen, or the like onto the laser processing portion, it is possible to improve the efficiency of removing the decomposition products.

  Further, the semiconductor wafer is cut by bonding one surface of the semiconductor wafer 8 to the adhesive sheet 3 provided on the suction stage 5 as shown in FIG. 4 and further providing the protective sheet 2 on the other surface side to obtain a predetermined laser oscillator. The laser beam 7 output from the laser beam is condensed and irradiated on the protective sheet 2 by a lens, and the laser irradiation position is moved along a predetermined processing line to perform cutting processing. As a laser beam moving means, a known laser processing method such as galvano scan, XY stage scan, mask, or imaging processing is used. The processing conditions for the semiconductor wafer are not particularly limited as long as the protective sheet 2 and the semiconductor wafer 8 are cut and the adhesive sheet 3 is not cut.

  In such a semiconductor wafer cutting process, after cutting into individual semiconductor chips, a method of picking up using a push-up pin called a needle by a conventionally known device such as a die bonder, or Japanese Patent Application Laid-Open No. 2001-118862. Individual semiconductor chips can be picked up and collected by a known method such as the method shown.

  In the laser processed product manufacturing method of the present invention, the protective sheet 2 is peeled from the laser processed product 10 after the laser processing is completed. The method of peeling is not limited, but it is important to prevent the laser-processed product 10 from undergoing stress that causes permanent deformation during peeling. For example, when a radiation curable pressure-sensitive adhesive is used for the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer is cured by irradiation with radiation according to the type of the pressure-sensitive adhesive, thereby reducing the adhesiveness. By the irradiation of radiation, the adhesiveness of the pressure-sensitive adhesive layer is reduced by curing, and peeling can be facilitated. The means for radiation irradiation is not particularly limited. For example, the irradiation is performed by ultraviolet irradiation.

  In the method for producing a laser processed product of the present invention, by using the protective sheet, a decomposition product generated from the laser light irradiation part adheres to the protective sheet surface covering the workpiece, It is possible to effectively prevent decomposition products from adhering. In addition, when a protective sheet having a high laser energy utilization efficiency with a light transmittance in the laser light absorption region of less than 50% is used, the protective sheet is eroded by the laser light before the workpiece, After the laser beam irradiation portion is eroded, the underlying workpiece is eroded. Therefore, since the decomposed material of the workpiece is scattered from the eroded portion of the protective sheet to the outside, contamination of the interface portion between the protective sheet and the workpiece can be suppressed. Therefore, according to the manufacturing method, the decomposed material does not adhere to the interface portion between the protective sheet and the workpiece (laser processed product). Therefore, after the workpiece is laser processed, the protective sheet is processed (laser processed). Can be easily peeled off from the product, and the laser processing accuracy of the workpiece can be improved.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

(Measurement of number average molecular weight)
The number average molecular weight of the synthesized (meth) acrylic polymer was measured by the following method. The synthesized (meth) acrylic polymer was dissolved in THF at 0.1 wt%, and the number average molecular weight was measured by polystyrene conversion using GPC (gel permeation chromatography). Detailed measurement conditions are as follows.
GPC device: Tosoh HLC-8120GPC
Column: manufactured by Tosoh Corporation, (GMH _HR −H) + (GMH _HR −H) + (G2000H _HR )
Flow rate: 0.8ml / min
Concentration: 0.1 wt%
Injection volume: 100 μl
Column temperature: 40 ° C
Eluent: THF

(Measurement of light transmittance)
The base material and the protective sheet were cut into arbitrary sizes, and U-3400 (manufactured by Hitachi, Ltd.) was used as a measuring device, and the light transmittance was measured at a measurement wavelength of 355 nm. In addition, about the protective sheet, it measured from the adhesive layer side.

Example 1
An acrylic pressure-sensitive adhesive that can be cured by ultraviolet rays on a base material (thickness: 20 μm, light transmittance at a wavelength of 355 nm: 0%) made of polyethylene naphthalate (weight ratio of aromatic ring in repeating unit: 64% by weight) The solution (1) was applied and dried to form an adhesive layer (thickness 10 μm) to obtain a protective sheet. The light transmittance of this protective sheet at a wavelength of 355 nm was 0%.

  The acrylic pressure-sensitive adhesive solution (1) was prepared by the following method. 100 parts by weight of an acrylic polymer having a number average molecular weight of 800,000 obtained by copolymerizing butyl acrylate / ethyl acrylate / 2-hydroxyethyl acrylate / acrylic acid at a weight ratio of 60/40/4/1, and dipentadiene as a photopolymerizable compound 90 parts by weight of erythritol monohydroxypentaacrylate and 5 parts by weight of benzyldimethyl ketal (Irgacure 651) as a photopolymerization initiator were added to 650 parts by weight of toluene, and uniformly dissolved and mixed to prepare an acrylic pressure-sensitive adhesive solution (1). .

  The protective sheet prepared above was bonded to one side of a 100 μm thick silicon wafer with a roll laminator to prepare a silicon wafer with a protective sheet. And the silicon wafer with a protection sheet was arrange | positioned on the XY stage on which the adsorption board made from glass epoxy resin was put. A third harmonic (355 nm) of a YAG laser having a wavelength of 355 nm, an average output of 5 W, and a repetition frequency of 30 kHz is condensed to a diameter of 25 μm on the surface of the silicon wafer with a protective sheet by an fθ lens, and the laser beam is 20 mm / second by a galvano scanner. Scanned and cut at speed. At this time, it was confirmed that the protective sheet and the silicon wafer were cut. Then, when the protective sheet was peeled and the laser processing peripheral part of the protective sheet bonding surface (laser beam incident surface side) of the silicon wafer was observed, no decomposition product (adhered matter) was observed.

Comparative Example 1
In Example 1, laser processing was performed on the silicon wafer in the same manner as in Example 1 except that the protective sheet was not provided on one side of the silicon wafer. Thereafter, when the surface of the silicon wafer on the laser light incident surface side was observed, a large amount of scattered residue was adhered.

Reference example 1
In Example 1, laser processing was performed on a silicon wafer in the same manner as in Example 1 except that a polyvinyl alcohol sheet (thickness: 50 μm, light transmittance at a wavelength of 355 nm: 84.4%) was used as the base material of the protective sheet. Was given. As a result, the protective sheet was not sufficiently cut, and the lower silicon wafer was laser processed, and bubbles containing decomposition product residues were generated between the protective sheet and the silicon wafer. When the protective sheet was peeled off and the periphery of the opening on the laser light incident surface side of the silicon wafer was observed, a decomposition residue of the silicon wafer was attached.

Example 2
An acrylic pressure-sensitive adhesive solution that can be cured by ultraviolet rays on a base material (thickness: 13 μm, light transmittance at a wavelength of 355 nm: 0%) made of polyimide (weight ratio of aromatic ring in repeating unit: 64% by weight) 2) was applied and dried to form an adhesive layer (thickness 10 μm) to obtain a protective sheet. The light transmittance of this protective sheet at a wavelength of 355 nm was 0%.

  The acrylic pressure-sensitive adhesive solution (2) was prepared by the following method. 20 parts by weight of 2-methacryloyloxyethyl isocyanate with respect to 100 parts by weight of an acrylic polymer having a number average molecular weight of 500,000 obtained by copolymerizing butyl acrylate / ethyl acrylate / 2-hydroxyethyl acrylate at a weight ratio of 50/50/16 Was added to introduce a carbon-carbon double bond into the polymer molecule inner chain (the length of the side chain at this time was 13 atoms). 100 parts by weight of this polymer, 1 part by weight of a polyisocyanate-based crosslinking agent (Coronate L), and 3 parts by weight of α-hydroxyketone (Irgacure 184) as a photopolymerization initiator are added to 350 parts by weight of toluene, and uniformly dissolved and mixed. An acrylic pressure-sensitive adhesive solution (2) was prepared.

  A circuit was formed on a two-layer substrate in which a copper layer having a thickness of 18 μm was formed on a polyimide film having a thickness of 25 μm by an exposure / development / etching process, thereby producing a flexible printed circuit board. The produced flexible printed circuit board and the said protective film were bonded together with the roll laminator, and the flexible printed circuit board with a protective sheet was produced.

  And the flexible printed circuit board with a protective sheet was arrange | positioned on the XY stage on which the ceramic suction plate made from alumina was put, the protective sheet surface facing up. A third harmonic (355 nm) of a YAG laser with a wavelength of 355 nm, an average output of 5 W, and a repetition frequency of 30 kHz is condensed to a 25 μm diameter on the surface of a flexible printed circuit board with a protective sheet by an fθ lens, and the laser light is 20 mm / second by a galvano scanner. Scanning and cutting at a speed of. At this time, it was confirmed that the protective sheet and the flexible printed board were cut. Then, when the protective sheet was peeled and the laser processing peripheral part of the protective sheet bonding surface (laser light incident surface side) of a flexible printed circuit board was observed, the decomposition product (adhered matter) was not observed.

Example 3
In Example 2, a polyethylene terephthalate film (weight ratio of aromatic ring in the repeating unit: 41% by weight, thickness: 50 μm, light transmittance at a wavelength of 355 nm: 44.9%) was used as the base material of the protective sheet. Was subjected to laser processing on the flexible printed circuit board in the same manner as in Example 2. As a result, it was confirmed that the protective sheet and the flexible printed board were cut. Then, when the protective sheet was peeled and the laser processing peripheral part of the protective sheet bonding surface (laser light incident surface side) of a flexible printed circuit board was observed, the decomposition product (adhered matter) was not observed.

Example 4
In Example 2, a polycarbonate film (weight ratio of aromatic ring in the repeating unit: 61% by weight, thickness: 20 μm, light transmittance at a wavelength of 355 nm: 0%) was used as the base material of the protective sheet. The flexible printed circuit board was subjected to laser processing in the same manner as in 2. As a result, it was confirmed that the protective sheet and the flexible printed board were cut. Then, when the protective sheet was peeled and the laser processing peripheral part of the protective sheet bonding surface (laser light incident surface side) of a flexible printed circuit board was observed, the decomposition product (adhered matter) was not observed.

Example 5
Polymer obtained by copolymerizing 4-methyl-1-pentene / 1,4-bis {2- [4- (N, N-di (p-tolyl) amino) phenyl] vinyl} benzene at a weight ratio of 97/3 Was formed into a sheet by casting to prepare a base material for a protective sheet.

  In Example 2, the above-prepared substrate (weight ratio of aromatic ring in the repeating unit: 2.4% by weight, thickness: 10 μm, light transmittance at a wavelength of 355 nm: 5%) is used as the substrate of the protective sheet. The flexible printed circuit board was subjected to laser processing in the same manner as in Example 2 except that. As a result, it was confirmed that the protective sheet and the flexible printed board were cut. Then, when the protective sheet was peeled and the laser processing peripheral part of the protective sheet bonding surface (laser light incident surface side) of a flexible printed circuit board was observed, the decomposition product (adhered matter) was not observed.

It is a schematic process drawing which shows the example of the manufacturing method of the laser processed product in this invention. It is a schematic process drawing which shows the other example of the manufacturing method of the laser processed product in this invention. It is the schematic which shows the cross section of the laminated body processed by the ultraviolet absorption ablation of a laser beam. It is the schematic which shows the example of the dicing method of a semiconductor wafer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Workpiece 2 Protection sheet for laser processing 3 Adhesive sheet 4 Laminate 5 Adsorption stage 6 Adsorption plate 7 Laser light 8 Semiconductor wafer 9 Dicing frame 10 Laser processed product

Claims (8)

A protective sheet for laser processing provided on the laser beam incident surface side of a workpiece when processing the workpiece by ultraviolet absorption ablation of laser light. The protective sheet for laser processing according to claim 1, wherein the light transmittance in the laser light absorption region is less than 50%. The protective sheet for laser processing according to claim 1 or 2, wherein the protective sheet is provided with an adhesive layer on a substrate. The protective sheet for laser processing according to claim 3, wherein the base material contains an aromatic polymer. The protective sheet for laser processing according to claim 4, wherein the weight ratio of the aromatic ring in the repeating unit constituting the aromatic polymer is 41% by weight or more. The step (1) of installing the protective sheet for laser processing according to any one of claims 1 to 5 on the laser light incident surface side of the workpiece, the protective sheet for laser processing and the workpiece by irradiating laser light A method for producing a laser-processed product, comprising: a step (2) for processing; and a step (3) for peeling the protective sheet for laser processing from the workpiece after processing. 7. The laser processed product according to claim 6, wherein the workpiece is a sheet material, a circuit board, a semiconductor wafer, a glass substrate, a ceramic substrate, a metal substrate, a semiconductor laser light emitting or receiving element substrate, a MEMS substrate, or a semiconductor package. Production method. The method of manufacturing a laser processed product according to claim 6 or 7, wherein the processing is cutting or drilling.

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